For clarification, this is Japanese porn.
It is illegal for uncensored porn to be sold within Japan since Western-style pornography. It was actually completely illegal in the 1940's-50's to make or distribute pornography however there were underground studios. Pictures or videos of full-frontal pubic hair AND genitalia is deemed unfit for distribution in the market. However, you get these type of crazy scenarios. Of course, like the 1950's, there are underground studios that develop uncensored porn. As expected, it is much easier to obtain legal porn then illegal.
Trust me, I have been living in Japan for 3 years now.